The invention relates to a system for manufacturing cement clinker from cement raw meal with a cyclone suspension-type heat exchanger system for preheating the raw meal, with a precalcination stage supplied with fuel and with tertiary air from the clinker cooler, with a sintering stage in the form of a rotary kiln and with the clinker cooler connected on the downstream side of the material flow, and with a rotary drum-type reactor for carbonizing/burning secondary fuels where the carbonization gases/combustion gases are introduced into the calcinator and the solid residues of the reactor are utilized in the cement clinker production line.
A cement clinker production line is known from document EP-A-0 764 614 with a separate shaft gasifier installed adjacent to the calcination system which is used as a secondary reactor, where coarse waste materials, especially used tires are gasified. The shaft gasifier is loaded from the top with the used tires and with a portion of the tertiary air coming from the clinker cooler as a gasification medium. The product gas generated in the shaft gasifier is introduced into the calcinator as fuel gas, and the residues of the used tires gasified in the shaft gasifier are transported to the inlet shaft of the rotary kiln by means of a mechanical push-off system. The gasification process in the shaft gasifier can be subject to considerable fluctuations because the used tires stacked in the shaft gasifier are not rearranged during the thermal treatment. No raw meal is introduced into the shaft gasifier where the waste materials, especially used tires are thermally treated.
A cement clinker production line is known from document WO 01/09548 where a separate reactor is installed adjacent to its calcinator. Said reactor is also loaded from the top with waste materials which are burned in the reactor with tertiary air from the clinker cooler. A partial stream of the cement raw meal is also introduced into the reactor from the top. The waste materials and the partial stream of raw meal are deposited in the combustion reactor on a rotating disk installed above the reactor bottom. By means of rotating the disk, the thermally treated solids are transferred outward and into the calcinator or the inlet of the rotary kiln. The combustion gas is also introduced into the calcinator. In said combustion reactor, the waste materials, especially coarse waste materials, are also not mixed so that uniform combustion conditions and thus a uniform raw meal precalcination cannot be expected.
According to document DE-C-35 33 775 in a system for manufacturing cement clinker from raw meal where waste materials having a calorific value are utilized, it is known to introduce the waste materials after they have been dried into a carbonizer operated by means of exit gas from the rotary kiln and a partial stream of the tertiary air for pyrolysis or for partially burning the waste materials, to introduce the pyrolysis gas into the calcinator and to treat and homogenize the solid pyrolysis residue and introduce it at least partially into the rotary kiln. In this case, the waste material carbonizer can also be configured as a rotary kiln. An introduction of cement raw meal into the carbonizer does not take place.
From documents DE-A-33 20 670, DE-A-34 11 144 and DE-A-35 20 447 in a system for manufacturing cement clinker where the waste materials having a calorific value are utilized, it is also known to carbonize or burn said waste materials in a separate rotary kiln and to use the carbonization gas/exit gas for the thermal treatment of the raw meal. However, no cement raw meal of any kind is introduced into the carbonizer/combustion furnace.
In the carbonization/burning of waste materials, however, especially coarse waste materials in a rotary kiln, it is difficult to provide uniform conditions for the thermal treatment, especially preventing temperature peaks which can lead to the baking on of solids in the rotary kiln, which is undesirable.
The object of the invention is to provide a cement clinker production line of the above described type with a calcinator connected to the rotary kiln and including a rotary drum-type reactor with the objective to safely burn even coarse secondary fuels, even including varying types and sizes, in the drum-type reactor and also to allow transferring the released heat energy evenly and effectively to the cement raw material, i.e., to be able to safely dispose of residues and produce cement clinker with favorable heat economics in one single integrated cement clinker production line.
First, the system of the invention for manufacturing cement clinker with a rotary drum-type reactor integrated in the calcination stage for carbonizing/burning and thus disposing of inert secondary fuels is characterized in that other than the secondary fuels and other than the partial stream of tertiary air coming from the clinker cooler, a partial stream of the cement raw meal also leads into the inlet opening for the material in the rotary drum-type reactor, especially preheated raw meal, which is related at least to the following advantages:
In the rotary drum-type reactor, the secondary fuel and the raw meal, which may already be very hot when it is introduced, are continuously circulated and mixed. As a result, the secondary fuels can be evenly distributed and effectively converted into the conversion products. The released heat energy is then transferred at least in part inside the rotary drum-type reactor directly and evenly to the partial stream of raw meal, which can then undergo a high-grade calcination at least in part inside the drum already, provided that the temperature in the rotary drum-type reactor is maintained at a level of at least approximately 800 to 850xc2x0 C. The thorough mixing of the carbonizing/burning secondary fuels, such as whole used tires, and the raw meal opens up the possibility of oxidizing the secondary fuels flameless so that no temperature peaks occur in the rotary drum, thereby minimizing the risk of solids baking on in the rotary drum. Moreover, with the quantity of raw meal added to the rotary drum-type reactor the temperature in the reactor can be controlled such that a melting phase of the solids is not produced. To this aim, even a partial stream of raw meal which is not preheated can be introduced into the rotary drum-type reactor. Also, there is a possibility that beginning in the rotary drum-type reactor already, certain pollutants of the secondary fuels are bound to the reactive cement raw meal.
It is also possible to provide the inside cover of the rotary drum-type reactor with lifting elements.
The exit side for the solids on the rotary drum-type reactor is connected to the tertiary air channel ascending from the bottom to the top and/or the rotary kiln exit gas channel of the calcinator by means of a line for discharging the carbonization gas/combustion gas-solids mixture, where the solids mixture consists of the solid residue of combustion, such as slag and the raw meal, which may be precalcinated. Coarse residues from the rotary drum-type reactor which cannot be pneumatically transported upward by the suspension flowing from the bottom to the top in the calcinator are introduced into the material inlet of the rotary clinker kiln and integrated into the clinker in the rotary clinker kiln so that the entire process produces no residues.
It is also possible, however, to introduce the mixture of solids exiting the rotary drum-type reactor, at least the coarse-grained components, directly into the inlet chamber of the rotary clinker kiln and/or directly into the clinker cooler.
Additionally, an igniter or starter burner can be inserted in the inlet side for the solids on the rotary drum-type reactor. Said starter burner is supplied with an easily ignitable fuel so as to start the rotary drum-type reactor. The exit gases of the rotary drum-type reactor are guided either as flue gas from the combustion or alternatively as combustible gas from the pyrolysis/carbonization of the secondary fuels into the calcinator and/or into the ascending line between the inlet chamber of the rotary kiln and the calcinator where they are used for further precalcination of the cement raw meal.
Furthermore, a partial stream of the exit gas from the rotary kiln containing pollutants can also be introduced into the rotary drum-type reactor. Said pollutants at least in part can be decomposed by and/or attached to the hot solids in the rotary drum-type reactor. The pollutants of the bypass gas can also be dioxins and/or furans, etc.